Does placing employees on furlough prevent the employer from making them redundant?

No, placing an employee on furlough does not prevent the employer from making them redundant.

HM Revenue and Customs (HMRC) guidance aimed at employees, Check if your employer can use the Coronavirus Job Retention Scheme, confirms that employers can make furloughed employees redundant during the period of furlough. There is no requirement for an employer to wait until the scheme ends before making redundancies.

The guidance for employees states that employers can continue to claim under the scheme while the employee is serving a statutory or contractual notice period. This would include where the employer has given employees notice of redundancy. (There has been inconsistency in the HMRC guidance for employers, which currently states that employers can claim during the statutory notice period, but no longer mentions contractual notice periods.)